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Mark August Sieron

Criminal defense Attorney at Green Cove Springs, FL

5.0   2 reviews
  • Licensed for 38 years
    State FL
    Acquired 1985
    Member in Good Standing No misconduct found

We have not found any instances of professional misconduct for this lawyer.

About Mark

Learn Mark’s areas of practice.

Practice areas
  1. Criminal defense
    A former state court prosecutor, Mark has been practicing criminal law for over 26 years in Florida. He is recognized by his peers, being assigned the highest possible rating by Martindale-Hubbel attroney rating servi9ce

    38 years

  2. Administrative law
    After entering private practice, Mark was local contract counsel to the Department of Business and Professional Regulation. He now defends professionals whose licenses are in jeapardy.

    35 years

  3. Litigation

I began my career as a prosecutor in the Fourth Judicial Circuit where I worked for legendary State Attorney Ed Austin. While there, I prosecuted cases ranging from DUI to murder. 

I left the State Attorney's Office to work as an associate for the firm of Kopelousos, Head, Smith, Townsend & Metcalf, a highly-respected AV- rated firm based in Clay County, Florida. After trying numerous criminal and complex civil cases, I became a shareholder in the firm which then became Head, Smith, Metcalf, Aguilar, Sieron & Moss, P.A. The current law firm is a successor to that firm.

Several years ago, I decided to concentrate primarily on criminal defense and associated administrative and civil cases.  I've been honored to have earned the respect of my peers and the judiciary, having received an AV-Preeminent rating (highest possible for legal ability and ethics) by Martindale-Hubbell for over 20 years.

Photos and videos

Contact Mark

Aguilar, Sieron & Yeomans, P.A
1045 North Orange Avenue
Green Cove Springs, FL, 32043-2529


5.0 / 5.0
  2 customer reviews
5 Star
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1 Star
Posted by Andrea | July 29, 2019
This review is from a person who hired this attorney.
| Hired Attorney
A Miracle Worker
When our family contacted Aguilar & Sieron, our son was in a desperate situation that other lawyers told us would lead to life...or, best case scenario, a 15-year or more sentence. But Mr. Sieron and his staff patiently and empathetically worked with us, assuring us that while things looked bleak, they had a plan to pursue the best outcome possible. We were able to avoid a messy trial and settle with a conditional release after just one year served. They took a seemingly impossible situation and turned it into a miracle that we are grateful for every day. We especially appreciate how Mr. Sieron took the time to clearly listen to our concerns and then fight for an agreement that best fit our specific situation. He is deeply connected in Florida, and those connections proved pivotal to securing the favorable release. We believe other lawyers simply couldn't have done what he was able to do. We highly recommend Aguilar & Sieron because of their expertise and knowledge of criminal law, as well as their good relationships and reputation in the community. Mr. Sieron, in particular, is not only a skilled professional, generous with his time and attention, but is also a compassionate and ethical person.
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Posted by anonymous | June 21, 2019
This review is from a person who hired this attorney.
| Hired Attorney
Mark Sieron is the best Criminal defense attorney in N Florida
Mark has represented me in a myriad of legal issues over the past 25 years. His knowledge and expertise is unmatched. He has always represented me honestly and tenaciously. He has protected my rights and always obtained an outcome that I was very satisfied with.


  • Retainer Always
Payment methods
Cash, Check, Credit Card


AVVO RATING 9.4 (Superb)

Work Experience

  • Managing Partner
  • Aguilar & Sieron,, P.A.
  • 2006 - Present
  • Associate/Shareholder
  • Kopelousos, Head, Smith, Townsend & Metcalf, P.A.
  • 1993 - 2006
  • Certified Intern
  • State Attorney's Office
  • 1984 - 1984
  • Prosecutor
  • State Attorney's Office
  • 1984 - 1987
  • Legal Intern
  • Law Offices of Ferrin Campbell, P.A.
  • 1983 - 1983
View all work experience


  • University of Florida
  • JD - Juris Doctor
  • 1984
  • University of Florida
  • BS - Bachelor of Science
  • 1981


  • Northeast Florida Association of Criminal Defense Lawyers
  • Member
  • 2005 - Present
  • Florida Association of Criminal Defense Lawyers
  • Member
  • 1996 - Present
  • National Association of Criminal Defense Lawyers
  • Member
  • 1996 - Present
  • Jacksonville Bar Association
  • Member
  • 1988 - Present
  • Clay County Bar Association
  • Past President
  • 1993 - 1995
  • Clay County Bar Association
  • Past President
  • 1990 - 1991
View all associations

Honors and Awards

  • AV Preeminent 5.0 out of 5 Peer Review Rated
  • Martindale-Hubbell
  • 2020
  • Super Lawyer
  • SuperLawyers
  • 2020
  • Super Lawyer
  • SuperLawyers
  • 2019
  • Top 100 Florida Trial Lawyers
  • National Trial Lawyers Association
  • 2014
  • Top Criminal Defense Lawyers
  • 904 Magazine
  • 2012
View all awards

Speaking Engagements

  • Florida Bar, Continuing Legal Education Committee
  • Third Party Liens
  • 1995
  • Different Career Paths
  • Small Firms vs, Big Firms
  • N/A

Attorney endorsements

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Green Cove Springs Criminal defense Lawyer Mark August Sieron
Mark August Sieron
Criminal defense Attorney
Green Cove Springs, FL
Licensed for 38 years